written 7.3 years ago by | modified 3.1 years ago by |
Mumbai University > Electronics Engineering > Sem 4 > Discrete Electronic Circuits
Marks: 10M
written 7.3 years ago by | modified 3.1 years ago by |
Mumbai University > Electronics Engineering > Sem 4 > Discrete Electronic Circuits
Marks: 10M
written 7.3 years ago by | • modified 7.3 years ago |
Given:
rd=40kΩ
kn=0.4×10−3
VGS(th)=3V
Av=−gm(rd||RD)
Rin=R1||R2
Ro=rd||RD
We know that,
gm=2kn(VGSQ−VT)
gm=2×0.4×10−3(VGSQ−3)……………..(1)
To find gmandVGSQ we have to perform DC analysis, all the coupling capacitor acts as open circuit, as shown in Figure 2:
IDS=kn(VGS−VT)2
IDS=0.4×10−3(VGS−3)2----------------(2)
But voltage divider biasing equation is,
VR2−VGS−(IDS×RS)=0
VGS=VR2−(IDS×1.2KΩ)----------------(3)
Using Voltage divider rule,
VR2=VGS=VDD×R2R1+R2
=30×10MΩ10MΩ+40MΩ
=6V
Substitute in equation (3),
VGS=6−(IDS×1.2KΩ)------------------(4)
Put equation (4) in (2),
IDS=0.4×10−3(6−(IDS×1.2KΩ)−3)2
IDS=0.4×10−3(3−IDS×1.2KΩ)2
Solving above equation we get two values of IDS,
IDS=5.625mAorIDS=1.11mA
IDS=5.625mA | IDS=1.11mA |
---|---|
VGS=6−(IDS×1.2KΩ)=6−(5.625mA×1.2KΩ)=−0.75V | VGS=6−(IDS×1.2KΩ)=6−(1.11mA×1.2KΩ)=4.668V |
−0.75V<VT | 4.668V>VT |
Hence from above observation, select IDSQ=1.11mAbecauseVGS>VT
Substitute in equation (4),
VGSQ=4.668V
Hence substitute VGSQ in equation (1),
gm=2×0.4×10−3(4.668−3)
gm=1.3344×10−3
Av=−gm(rd||RD)
Av=−1.3344×10−3(40kΩ||3.3KΩ)
Av=-4.06
Rin=R1||R2
Rin=40MΩ||10MΩ
Rin=8MΩ
Ro=rd||RD
Ro=40MΩ||3.3KΩ
Ro=3.048KΩ